Pursuing A Stealthy Germ That Causes Dangerous Infections

Thursday, May 24, 2012

In the past few weeks, a “flesh-eating bacteria,” or necrotizing fasciitis, has been making headlines because it has seriously affected three people. However, this type of infection is very rare. More common are infections in children caused by methicillin-resistant Staphylococcus aureus (MRSA). And they’re on the rise.

Infections Become a Family AffairOver the last decade, there has been a dramatic increase in the number of infections from MRSA in otherwise healthy children in the community. MRSA is the most frequent cause of skin infections and invasive, life-threatening infections of the muscles and bones in children. In addition, MRSA infections often affect multiple family members in a household.

Researcher Stephanie Fritz, MD, MSCI, is seeking answers about MRSA. Through her research at the Children’s Discovery Institute, a research partnership between St. Louis Children’s Hospital and Washington University School of Medicine, Dr. Fritz is unraveling the epidemiology of these MRSA infections and informing clinicians about best practices to eradicate the organism from patients and households.

Dr. Fritz’s interest in MRSA began while she was working at St. Louis Children’s Hospital during her fellowship in pediatric infectious diseases at Washington University School of Medicine. “We were seeing five kids a day with Staph infections and patients frequently had multiple recurrent infections,” she says. “Because of that, we started a separate clinic to focus specific expertise on this problem.”

At St. Louis Children’s Hospital, Dr. Fritz says doctors treat nearly 1,200 children a year for skin abscesses, the majority of which are caused by MRSA, and another 50 children with invasive Staph infections. She says even superficial skin infections from MRSA require painful draining procedures. And more children are acquiring severe staph infections in the bones or joints or have pneumonia caused by MRSA.

“My experience in the clinic piqued my interest in why MRSA infections have become such a problem,” Dr. Fritz says.

Her curiosity led to several research projects on the epidemiology and prevention of MRSA colonization, infection and transmission. She collaborated with community pediatricians through the Washington University Pediatric and Adolescent Ambulatory Research Consortium to collect data from 1,300 children. “What struck me was that we frequently saw multiple skin infections caused by MRSA in the same households,” Dr. Fritz says.

The research group shows that children were at seven times higher risk for developing a skin infection if a household member had a recent Staph infection. “I wanted to know: if we get rid of MRSA from the skin, can we prevent recurrence in the family household?” Dr. Fritz says.

Stopping a “Worst-Case Germ”MRSA is a puzzling foe. Some people carry the bacteria in their nose and on the skin yet have no infection. However, they can pass this bacteria to others who do get an infection.

Dr. Fritz says MRSA is a “worst-case germ” because it’s particularly hardy. It can live for months at a time on environmental surfaces compared to many other germs that can only live on surfaces for a matter of hours.

MRSA also is easily transmitted, which is one reason why it’s becoming a growing problem. Current MRSA comes in two general types. The first is an aggressive strain that is acquired in the community by patients with no prior hospital exposure. The second is a hospital-acquired strain of MRSA that is more resistant to antibiotics. By culturing the bacteria, physicians can tell which type of bacteria they are dealing with. “The good news is the MRSA in households responds well to antibiotics,” Dr. Fritz says. “However, MRSA infections can be extremely painful and they can lead to invasive infections and even cause death if they are not treated.”

In Dr. Fritz’s study of preventing MRSA infections in households, special soap and antibiotic ointment were given to either just the patient who had a MRSA infection or to the patient’s entire family to use at home. Dr. Fritz and her colleagues found that if the entire household followed the five-day regimen, the occurrence of recurrent MRSA was reduced. However, MRSA still recurred in the household over the course of a year.

Finding Answers in the Genes“Now we’re asking what makes a household susceptible to MRSA,” Dr. Fritz says. “Did the family members share things such as razors, towels and beds? Or is MRSA living on environmental surfaces such as refrigerator door handles or countertops or on household pets? Through Children’s Discovery Institute funding, we’re asking why Staph lives on the skin of some people who never develop symptomatic infection, while it leads to infection in others? Is it something about the germ or the person’s immune system? Or is it the perfect storm of genes in the person and the germ and the environment?”

Clearly, there are many questions to be answered. Dr. Fritz is collaborating with other Washington University researchers to use genetic information to interrogate these and discover the key players in MRSA infection. “In the future, it will be helpful to know if people are at higher risk for more invasive MRSA infections,” she says. “If so, we could use interventions more aggressively and this information would guide therapy when patients come to the hospital. In the near future, we hope to know how MRSA is transmitted in households and what helps to stop it. This information could be useful for other infectious diseases, as well.”

Because of her important research on this stealthy germ, Dr. Fritz recently received the 2012 Young Investigator Award from the Pediatric Infectious Diseases Society (PIDS).

The Young Investigator Award honors and recognizes young physicians for outstanding contributions in clinical or basic research in the field of pediatric infectious diseases. Dr. Fritz was honored for her clinical and translational studies of pediatric colonization and infection with MRSA.

As a Children’s Discovery Institute Faculty Scholar, Dr. Fritz’s research is supported by the Institute. “It’s truly an honor to be acknowledged by my peers for this award,” Dr. Fritz says. “I’ve been fortunate to have excellent mentors and support along with great collaborators and resources.”

She continues: “As junior investigators, we have many creative ideas. The Children’s Discovery Institute takes a chance on us so we can explore these creative avenues and hopefully bring a large return on their investment. The breadth of research at the Institute is so amazing. It’s research that’s going to make a difference in the lives of children.”